I'm gonna need more time to think of something for now to WM 31.
It terms of "rewriting," I know it's not the popular choice, but Reigns would've won the title at WM. On the next RAW, Reigns should've given his speech and Lesnar should've attacked him, the camera man, and the announce team. They could've given Reigns a kayfabe injury (freakin wrapped up ribs, crutches, fake neck brace and all), he would've returned the next week, vowing to kick Lesnar's ass once his ribs and neck got better, "believe that." The Authority would come along to try and pull a Daniel Bryan on him, trying to force him to give up his title. Reigns refuses and accepts The Authority and Rollins' challenge at Extreme Rules. They get in the match, Reigns whoops Rollins to a pulp with his neck brace and crutches and wins the match. The authority ain't done though, they still want their title back. They get Rollins' new lapdog, not the old Kane, but Kevin Owens, to attack Reigns. Ambrose to the rescue. However, over the next few months, the authority beat Reigns that by the time he makes it to Summerslam, he's no match for Lesnar. During the rematch, Rollins should've cashed in his suitcase and won. Lesnar could then take another 3 month vacation, and Reigns and Rollins would've carried the show throughout until The Rock shows up and grill Triple H and Steph about the treatment of his cousin. WHAT? Then Ronda would come out of the crowd again and this time beat Stephanie's ass, leading us into the Royal Rumble. 3 man, mix gender, tag match with Reigns, Rock and Ronda vs Rollins, HHH and Steph. Then Ambrose would win the Royal Rumble, setting up build up for the shield main event WM 31. But Lesnar is not done, in his pursuit to destroy Reigns for beating him at mania and Rollins for stealing the title at SS, Lesnar destroys Ambrose in some attack on RAW. The Shield brothers are mad and have one thing in common: Lesnar. So Heyman books a handicap match at the PPV before mania. The Shield vs Lesnar. They take down the beast and win the match. They all watch each other, because the road to WM goes through any one of them.
Since those plans were butchered by creative. I have to rewrite what should happen again. I'll have more for the main event and the rest of the show tomorrow.